Generator regulation



Patented Apr. 19, 1949 GENERATOR REGULATION Joseph William Allen, Washington, D. 0.

Application April 23, 1945, Serial No. 589,831

(Granted under the act of March 3, 1883, as amended April 30, 1928; 370 0. G. 757) 3 Claims.

This invention relates to voltage regulators for electric generators, more particularly of the carbon pile type, adapted for use with generators having a considerable range of field current.

It is'an object of the present invention to provide means to increase the applicability of regulators having low resistance carbon piles designed for high field current generators so they will function satisfactorily with low field current generators.

Another object is to provide means that will materially reduce the number of types of regulators necessary to stock to equip generators operating with different strengths of field currents.

A further object is to provide means that will automatically adjust the resistance in the generator field circuit to the strength oi the current therein.

The drawing depicts schematically one embodiment of this invention.

The types of voltage regulators used for aircraft. generators, especially regulators of the carbon pile type, require that the regulators be matched to the generators primarily because a resistance that is suitable for a high field current generator is too small for a low field current generator. A low value of resistance, when the pile is compressed, is necessary for high field current generators. The working range of a carbon pile is limited by a fairly definite ratio between its high resistance value at a low pressure and its low resistance value at a high pressure. A much higher resistance at low pressures is needed for low field current generators than is available in the piles customarily used for high field current generators.

By way of specific examples, but without im-= porting any limitations as to the present invention, the carbon pile for high field current gen= erators is required to have a high resistance value of approximately 15 ohms and a low resistance value, at higher pressures, of approximately ohm. Regulators for low field current generators require a high resistance value of approximately 60 ohms with a low resistance value of about 2' ohms at high pressure. It is necessary at the present time to use voltage regulators having carbon piles with three different ranges of resistance and to match a regulator with the proper resistance value of carbon pile to each generator.

The present invention contemplates a single regulator that will automatically provide the approximate resistance required by any of the types of generators in use. The carbon pile has a low resistance such as is normally used only for high field current generators but, as a function of field current amperes, will progressively insert additional resistance in the field circuit as the shunt field current decreases.

Specific values of resistance and ampere turns will be set forth but these are by way of illustration only and not of limitation. Also, while specific reference is made to the use of the present invention in connection with an aircraft gener ator its usefulness is not limited thereto.

The device comprises what is essentially a normally closed magnetic switch I having two coils or windings 2 and 3. Winding 2 is a potential or voltage winding providing a substantially constant value of ampere turns at the voltage that is being maintained by the voltage regulator. Winding 3 is in series with shunt field 4 of gen erator 5 through the carbon pile 6 and provides a value of ampere turns proportional to the current in field 4. Windings 2 and 3 are so connected into the circuit that the fluxes produced thereby oppose each other. For example, if winding 2 produces 600 ampere turns at 30 volts and winding 3 produces ampere turns at 2 amperes field current the resultant ampere turns for providing magnetic flux is 600 minus 100 equals 500 ampere turns.

Windings 2 and 3 are disposed around a core constituting one leg of a substantially U-shaped member d to the other leg 9 of which is pivotaliy mounted the armature iii. Spring ii biases the armature lli away from the core I in opposition to the attraction exerted by the magnetic flux. Fixed to the same end of armature ID as that to which the spring I i is connected is a contact arm. it which sweeps over and closes the circuit through the contacts 13 that are connected to spaced points along resistor [4 that is in series with winding 3, carbon pile 6 and generator field winding Q. The arm i2 is connected by wire to generator lead it so that as the resultant flue: set up by coils 2 and 3 varies and armature it is moved with respect to core I, the number of sections of resistor l4 effectively in series with the generator field is varied.

Let it be assumed, by way of illustration, that resistor 64 has a total value of 50 ohms and that each segment thereof has a resistance of 10 ohms and that when no current is flowing the arm i2 is so positioned by spring ii that the resistor M is completely shorted out of the circuit. Assume further, that at 2 amperes field current the armature I0 is attracted to insert the first 10 ohm section of resistor l4 into the field circuit and that this occurs at 600 ampere turns minus 100 ampere insertion of the remaining sections of the resistor can be arranged substantially as follows:

2 amperes field 600l 500 A. T., add 1st 10 ohm section 1}; ampores fieid, 600-75=525 A. T., add 2nd 10 ohm section 1 ampere ileld, 60050=550 A. T., add 3rd 10 ohm SeCtlOIl .75 ampere field, 60037.6==662.5 A. T. add 4th 10 ohm section .5 ampere field, 60025=576 A. T., add 5th ohm section It is apparent that with a low resistance car= bon pile s, having a resistance range or /2 to ohms, the resistor it and associated means provide a total resistance range of from to 65 ohms in the field circuit of generator 5. since the resistance values are inserted as a function of the strength or the generator field current, the combination of a low resistance carbon pile regulator and the resistance insertion device above described can he used with generstore of high, medium and low field current values. When used with high field current generators none of the resistance it may be added to the field circuit; with medium field generators possibly up to 2 or 3 sections of the resistance i4 may be added and with low field current generators the entire resistance is would be included in the circuit.

It is within the purview of this invention that instead of step-by-step insertion of sections of resistor as into the field circuit a continuous change of resistance may be eflectedby making resistor as arcuate in form and having arm 52 contact directly therewith as in an ordinary rheostat.

The carbon pile regulator may be of conventional type comprising a stressed spring ll to apply pressure to the carbon pile 6, and armature l8 attached to the spring ii and a voltage coil is to attract armature it proportionally to the output voltage of generator 5 and thereby vary the pressure upon the carbon pile 6 which, as is well known, changes the resistance of the carbon pile.

This device therefore provides a means for utilizing only one regulator for all generators resulting in higher production of regulators, complete interchangeability of parts, decrease in maintenance problems and ready replacement of defective regulators without extreme care being taken that the proper regulator is being installed. The device permits use of a regulator with a low resistance value where high resistances are required permitting the manufacture and stocking of only one assembly of carbon discs.

The invention described herein may be manufactured'and used by or for the Government of the United States of America for govemmental purposes without the payment of any royalties thereon or therefor.

I claim:

1. A system for regulating the output voltage of a generator having a shunt field winding connected at one side to a terminal of the genera-' tor, comprising a carbon pile regulator, a resistance, and a current coil all three in series between the other side of said winding and the other terminal of the generator, a plurality of contacts each respectively connected to a different point on the resistance, a core in said coil, a voltage coil connected across the generator and also disposed around the core, the voltage coil providing a stronger flux than the current coil in opposition to the flux of the current ill) coil, an armature pivoted intermediate its ends having one end disposed to be attracted by the resultant flux in the core, a spring connected to said armature to bias the armature away from the core, a conductive element electrically connected to said other terminal of the generator and mounted on the other end of said armature to close a circuit through some one of said contaste to vary the portion of the resistance eifectively included in the field circuit as the a m. ture is moved by said core or said spring, means to apply pressure to the carbon pile, and a second voltage coil connected across the generator and disposed to vary the pressure applied by said means to the carbon pile in response to changes in said output voltage.

2. A system ior regulating the output voltage of a generator having a shunt field winding connected at one side to a terminal of the generator, comprising a carbon pile regulator, a resistance, and a current coil all three in series between the other side of said winding and the other terminal of the generator, a plurality of contacts each respectively connected to a difierent point on the resistance, a core in said coil, a voltage coil connected across the generator and also disposed-around the core, the voltage coil providing a stronger flux than the current coil in opposition to the fiux of the currrent coil. means responsive to the resultant flux of the current coil and the voltage coil to vary the portion of the resistance efiectively included in the field circuit, means to apply pressure-to the carbon pile, and a second voltage coil connected across the generator and disposed to vary the pressure applied by said means to the carbon "pile in response to changes in said output voltage.

3. A system for regulating the output voltage of a generator having a shunt field winding connected at one side to a terminal of the genera tor, comprising a carbon pile regulator, a variable resistance, and a current coil all three in series between the other side of said winding and the other terminal of the generator, a core in said coil, a voltage coil connected across the generator and also disposed around the core, the voltage coil providing a stronger flux than the current coil in opposition to the flux of the current coil,

means responsive to the resultant flux of the current coil and the voltage coil to vary the portion of the resistance effectively included in the field circuit, and electrical means including a voltage responsive device connected across the generator to apply a variable pressure to the carbon pile.

JOSEPH 'I' ALLEN.

REFERENGES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS 

